/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * libc/wqueue/work_usrthread.c
 *
 *   Copyright (C) 2009-2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <stdint.h>
#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
#include <assert.h>
#include <queue.h>

#include <tinyara/wqueue.h>
#include <tinyara/clock.h>

#include "wqueue/wqueue.h"

#if defined(CONFIG_LIB_USRWORK) && !defined(__KERNEL__)

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Use CLOCK_MONOTONIC if it is available.  CLOCK_REALTIME can cause bad
 * delays if the time is changed.
 */

#ifdef CONFIG_CLOCK_MONOTONIC
#define WORK_CLOCK CLOCK_MONOTONIC
#else
#define WORK_CLOCK CLOCK_REALTIME
#endif

#ifndef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Public Data
 ****************************************************************************/

/* The state of the user mode work queue. */

struct usr_wqueue_s g_usrwork;

/* This semaphore supports exclusive access to the user-mode work queue */

#ifdef CONFIG_BUILD_PROTECTED
sem_t g_usrsem;
#else
pthread_mutex_t g_usrmutex;
#endif

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: work_process
 *
 * Description:
 *   This is the logic that performs actions placed on any work list.  This
 *   logic is the common underlying logic to all work queues.  This logic is
 *   part of the internal implementation of each work queue; it should not
 *   be called from application level logic.
 *
 * Input parameters:
 *   wqueue - Describes the work queue to be processed
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void work_process(FAR struct usr_wqueue_s *wqueue)
{
	volatile FAR struct work_s *work;
	worker_t worker;
	FAR void *arg;
	systime_t elapsed;
	uint32_t remaining;
	systime_t stick;
	systime_t ctick;
	uint32_t next;
	int ret;

	/* Then process queued work.  Lock the work queue while we process items
	 * in the work list.
	 */

	next = wqueue->delay;
	ret = work_lock();
	if (ret < 0) {
		/* Break out earlier if we were awakened by a signal */

		return;
	}

	/* Get the time that we started this polling cycle in clock ticks. */

	stick = clock_systimer();

	/* And check each entry in the work queue.  Since we have locked the
	 * work queue we know:  (1) we will not be suspended unless we do
	 * so ourselves, and (2) there will be no changes to the work queue
	 */

	work = (FAR struct work_s *)wqueue->q.head;
	while (work) {
		/* Is this work ready?  It is ready if there is no delay or if
		 * the delay has elapsed. qtime is the time that the work was added
		 * to the work queue.  It will always be greater than or equal to
		 * zero.  Therefore a delay of zero will always execute immediately.
		 */

		ctick = clock_systimer();
		elapsed = ctick - work->qtime;
		if (elapsed >= work->delay) {
			/* Remove the ready-to-execute work from the list */

			(void)dq_rem((struct dq_entry_s *)work, &wqueue->q);

			/* Extract the work description from the entry (in case the work
			 * instance by the re-used after it has been de-queued).
			 */

			worker = work->worker;

			/* Check for a race condition where the work may be nullified
			 * before it is removed from the queue.
			 */

			if (worker != NULL) {
				/* Extract the work argument (before unlocking the work queue) */

				arg = work->arg;

				/* Mark the work as no longer being queued */

				work->worker = NULL;

				/* Do the work.  Unlock the the work queue while the work is being
				 * performed... we don't have any idea how long this will take!
				 */

				work_unlock();
				worker(arg);

				/* Now, unfortunately, since we unlocked the work queue we don't
				 * know the state of the work list and we will have to start
				 * back at the head of the list.
				 */

				ret = work_lock();
				if (ret < 0) {
					/* Break out earlier if we were awakened by a signal */

					return;
				}

				work = (FAR struct work_s *)wqueue->q.head;
			} else {
				/* Cancelled.. Just move to the next work in the list with
				 * the work queue still locked.
				 */

				work = (FAR struct work_s *)work->dq.flink;
			}
		} else {				/* elapsed < work->delay */

			/* This one is not ready.
			 *
			 * NOTE that elapsed is relative to the the current time,
			 * not the time of beginning of this queue processing pass.
			 * So it may need an adjustment.
			 */

			elapsed += (ctick - stick);
			if (elapsed > work->delay) {
				/* The delay has expired while we are processing */

				elapsed = work->delay;
			}

			/* Will it be ready before the next scheduled wakeup interval? */

			remaining = work->delay - elapsed;
			if (remaining < next) {
				/* Yes.. Then schedule to wake up when the work is ready */

				next = remaining;
			}

			/* Then try the next in the list. */

			work = (FAR struct work_s *)work->dq.flink;
		}
	}

	/* Get the delay (in clock ticks) since we started the sampling */

	elapsed = clock_systimer() - stick;
	if (elapsed < wqueue->delay && next > 0) {
		/* How must time would we need to delay to get to the end of the
		 * sampling period?  The amount of time we delay should be the smaller
		 * of the time to the end of the sampling period and the time to the
		 * next work expiry.
		 */

		remaining = wqueue->delay - elapsed;
		next = MIN(next, remaining);

		/* Wait awhile to check the work list.  We will wait here until
		 * either the time elapses or until we are awakened by a signal.
		 * Interrupts will be re-enabled while we wait.
		 */

		usleep(next * USEC_PER_TICK);
	}

	work_unlock();
}

/****************************************************************************
 * Name: work_usrthread
 *
 * Description:
 *   This is the worker thread that performs the actions placed on the user
 *   work queue.
 *
 *   This is a user mode work queue.  It must be used by applications for
 *   miscellaneous operations.  The user work thread must be started by
 *   application start-up logic by calling work_usrstart().
 *
 * Input parameters:
 *   argc, argv (not used)
 *
 * Returned Value:
 *   Does not return
 *
 ****************************************************************************/

#ifdef CONFIG_BUILD_PROTECTED
static int work_usrthread(int argc, char *argv[])
#else
static pthread_addr_t work_usrthread(pthread_addr_t arg)
#endif
{
	/* Loop forever */

	for (;;) {
		/* Then process queued work.  We need to keep the work queue locked
		 * while we process items in the work list.
		 */

		work_process(&g_usrwork);
	}

#ifdef CONFIG_BUILD_PROTECTED
	return OK;					/* To keep some compilers happy */
#else
	return NULL;				/* To keep some compilers happy */
#endif
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: work_usrstart
 *
 * Description:
 *   Start the user mode work queue.
 *
 * Input parameters:
 *   None
 *
 * Returned Value:
 *   The task ID of the worker thread is returned on success.  A negated
 *   errno value is returned on failure.
 *
 ****************************************************************************/

int work_usrstart(void)
{
	/* Initialize work queue data structures */

	g_usrwork.delay = CONFIG_LIB_USRWORKPERIOD / USEC_PER_TICK;
	dq_init(&g_usrwork.q);

#ifdef CONFIG_BUILD_PROTECTED
	{
		/* Set up the work queue lock */

		(void)sem_init(&g_usrsem, 0, 1);

		/* Start a user-mode worker thread for use by applications. */

		g_usrwork.pid = task_create("uwork", CONFIG_LIB_USRWORKPRIORITY, CONFIG_LIB_USRWORKSTACKSIZE, (main_t)work_usrthread, (FAR char *const *)NULL);

		DEBUGASSERT(g_usrwork.pid > 0);
		if (g_usrwork.pid < 0) {
			int errcode = errno;
			DEBUGASSERT(errcode > 0);
			return -errcode;
		}

		return g_usrwork.pid;
	}
#else
	{
		pthread_t usrwork;
		pthread_attr_t attr;
		struct sched_param param;
		int status;

		/* Set up the work queue lock */

		(void)pthread_mutex_init(&g_usrmutex, NULL);

		/* Start a user-mode worker thread for use by applications. */

		(void)pthread_attr_init(&attr);
		(void)pthread_attr_setstacksize(&attr, CONFIG_LIB_USRWORKSTACKSIZE);

		param.sched_priority = CONFIG_LIB_USRWORKPRIORITY;
		(void)pthread_attr_setschedparam(&attr, &param);

		status = pthread_create(&usrwork, &attr, work_usrthread, NULL);
		if (status != 0) {
			return -status;
		}

		/* Detach because the return value and completion status will not be
		 * requested.
		 */

		(void)pthread_detach(usrwork);

		g_usrwork.pid = (pid_t)usrwork;
		return g_usrwork.pid;
	}
#endif
}

#endif							/* CONFIG_LIB_USRWORK && !__KERNEL__ */
